Investigating neuroinflammation and demyelination in the nervous system of Twitcher mice by the use of immunohistochemistry

Author

Irene Wilson, Dominican University of CaliforniaFollow

Graduation Year

2019

Document Type

Master's Thesis

Degree

Master of Science

Program

Biological Science

Program Director

Meredith Protas, PhD

First Reader

Silvia Sisó-Llonch, DVM, PhD

Second Reader

Kristylea Ojeda, PhD

Abstract

Neuroinflammation and demyelination are the hallmark lesions of the Twitcher mouse—the model of Krabbe Disease. By analyzing hemibrains and sciatic nerves via immunohistochemistry, we supported the microglial hypothesis that early activation of microglial cells, macrophages, and globoid cells in the nervous system of Twitcher mice results in specific cellular polarization states that may contribute to myelin loss. The influx of activated macrophages seen in both the central and peripheral nervous systems at days 21 and 17, respectively, accounted for this polarization. Using selected M1 and M2 markers, YKL-40, and GPNMB and CD206, respectively, we proved that microglial cells and macrophages sustain an anti-inflammatory immune response in Twitcher mice, which occurs before the onset of demyelination. The onset of segmental demyelination was only rarely detected in the nervous system of terminally ill Twitcher mice. Remarkably, both the central and peripheral nervous systems showed reduced myelination rates by 14 days, with a surplus of non-myelinating cells populating the Twitcher central nervous system. Polydendrocytes, however, appear to be reduced in the adult Twitcher brain in conjunction with reduced neurogenesis. This thesis successfully designed an immunohistochemical algorithm to characterize the pathogenesis of the nervous system, in particular of microglial cells, monocytes, and macrophages, as well as the immune profile of globoid cells. Reduced wild-type levels of myelination and neurogenesis may point toward defects in brain development. Providing the research community with an array of suitable markers to characterize the immunophenotype of activated microglial cells and macrophages, as well as the maturation state of oligodendroglial cells, assists researchers in comprehending Krabbe Disease, as well as other neurodegenerative diseases. Moreover, it brings the community closer to developing a therapeutic target.